The initial region of subsonic coaxial jets. Part 2

Abstract

Earlier investigations by the authors have suggested that coherent structures, in the form of two different arrays of vortices, exist in the initial region of coaxial jets. The present investigation was aimed at obtaining further information on the characteristics of the vortices in coaxial jets. Single- and two-point correlation covariance measurements of the fluctuating pressure and the axial and radial velocity fluctuations have been made in the initial region of coaxial jets. Detailed analysis of the correlograms indicates the combined effect of the two vortex trains on the correlograms. Further, the analysis enables the phase relationship between the pressure and axial and radial velocity fluctuations to be obtained. From the correlation results the phase properties obtained within the whole initial region of coaxial jets are found to agree with the results for single jets. This good agreement supports the formally suggested simple approach to the understanding of the complicated flow in coaxial jets.